-40 70 2500 20 (2500) (1000) 40 MINIMUM DESIGN LOADS (700) 40 CS (1700 (800) 1200) (700 HOO 500) (500) 50 1900) 50 (600) 80 (500) TO 2.1 GENERAL Buildings and other structures shall be designed using the provisions of either Section 2.3 or 2.4. Where elements of a structure are designed by a particular material standard or specification, they shall be designed exclusively by either Section 2.3 or 2.4. 2.2 SYMBOLS A = load or load effect arising from extra ordinary event A D = dead load D; weight of ice = E = earthquake load F = load due to fluids with well-defined pressures and maximum heights flood load Fa H = load due to lateral earth pressure, ground water pressure, or pressure of bulk materials L = live load L, roof live load R = rain load S = snow load T = self-straining load W wind load W; wind-on-ice determined in accordance with Chapter 10 2.3 COMBINING FACTORED LOADS USING STRENGTH DESIGN 2.3.1 Applicability The load combinations and load factors given in Section 2.3.2 shall be used only in those cases in which they are specifically authorized by the appli- cable material design standard. 2.3.2 Basic Combinations Structures, components, and foundations shall be designed so that their design strength equals or exceeds the effects of the factored loads in the following combinations: 1. 1.4D 2. 1.2D 1.6L + 0.5(L, or S or R) 3. 1.2D 1.6(L, or S or R) + (L or 0.5W) 4. 1.2D 1.0W+L+ 0.5(L, or S or R) 5. 1.2D 1.0E+L+ 0.2S 6. 0.9D1.0W 7. 0.9D+1.0E EXCEPTIONS: 1. The load factor on L in combinations 3, 4, and 5 is permitted to equal 0.5 for all occupancies in which L, in Table 4-1 is less than or equal to 100 psf, with the exception of garages or areas occupied as places of public assembly. 2. In combinations 2, 4, and 5, the companion load S shall be taken as either the flat roof snow load (p) or the sloped roof snow load (p.). Where fluid loads F are present, they shall be included with the same load factor as dead load D in combinations 1 through 5 and 7. Where load H are present, they shall be included as follows: 1. where the effect of H adds to the primary variable load effect, include H with a load factor of 1.6; 2. where the effect of H resists the primary variable load effect, include H with a load factor of 0.9 where the load is permanent or a load factor of 0 for all other conditions. Effects of one or more loads not acting shall be investigated. The most unfavorable effects from both wind and earthquake loads shall be investigated, where appropriate, but they need not be considered to act simultaneously. Refer to Section 12.4 for specific definition of the earthquake load effect E.' Each relevant strength limit state shall be investigated. 2.3.3 Load Combinations Including Flood Load When a structure is located in a flood zone (Section 5.3.1), the following load combinations shall be considered in addition to the basic combinations in Section 2.3.2: 1. In V-Zones or Coastal A-Zones, 1.0W in combina- tions 4 and 6 shall be replaced by 1.0W + 2.0F. 2. In noncoastal A-Zones, 1.0W in combinations 4 and 6 shall be replaced by 0.5W + 1.0Fa 'The same E from Sections 1.4 and 12.4 is used for both Sections 2.3.2 and 2.4.1. Refer to the Chapter 11 Commentary for the Seismic Provisions. 7 |
-40 70 2500 20 (2500) (1000) 40 MINIMUM DESIGN LOADS (700) 40 CS (1700 (800) 1200) (700 HOO 500) (500) 50 1900) 50 (600) 80 (500) TO 2.1 GENERAL Buildings and other structures shall be designed using the provisions of either Section 2.3 or 2.4. Where elements of a structure are designed by a particular material standard or specification, they shall be designed exclusively by either Section 2.3 or 2.4. 2.2 SYMBOLS A = load or load effect arising from extra ordinary event A D = dead load D; weight of ice = E = earthquake load F = load due to fluids with well-defined pressures and maximum heights flood load Fa H = load due to lateral earth pressure, ground water pressure, or pressure of bulk materials L = live load L, roof live load R = rain load S = snow load T = self-straining load W wind load W; wind-on-ice determined in accordance with Chapter 10 2.3 COMBINING FACTORED LOADS USING STRENGTH DESIGN 2.3.1 Applicability The load combinations and load factors given in Section 2.3.2 shall be used only in those cases in which they are specifically authorized by the appli- cable material design standard. 2.3.2 Basic Combinations Structures, components, and foundations shall be designed so that their design strength equals or exceeds the effects of the factored loads in the following combinations: 1. 1.4D 2. 1.2D 1.6L + 0.5(L, or S or R) 3. 1.2D 1.6(L, or S or R) + (L or 0.5W) 4. 1.2D 1.0W+L+ 0.5(L, or S or R) 5. 1.2D 1.0E+L+ 0.2S 6. 0.9D1.0W 7. 0.9D+1.0E EXCEPTIONS: 1. The load factor on L in combinations 3, 4, and 5 is permitted to equal 0.5 for all occupancies in which L, in Table 4-1 is less than or equal to 100 psf, with the exception of garages or areas occupied as places of public assembly. 2. In combinations 2, 4, and 5, the companion load S shall be taken as either the flat roof snow load (p) or the sloped roof snow load (p.). Where fluid loads F are present, they shall be included with the same load factor as dead load D in combinations 1 through 5 and 7. Where load H are present, they shall be included as follows: 1. where the effect of H adds to the primary variable load effect, include H with a load factor of 1.6; 2. where the effect of H resists the primary variable load effect, include H with a load factor of 0.9 where the load is permanent or a load factor of 0 for all other conditions. Effects of one or more loads not acting shall be investigated. The most unfavorable effects from both wind and earthquake loads shall be investigated, where appropriate, but they need not be considered to act simultaneously. Refer to Section 12.4 for specific definition of the earthquake load effect E.' Each relevant strength limit state shall be investigated. 2.3.3 Load Combinations Including Flood Load When a structure is located in a flood zone (Section 5.3.1), the following load combinations shall be considered in addition to the basic combinations in Section 2.3.2: 1. In V-Zones or Coastal A-Zones, 1.0W in combina- tions 4 and 6 shall be replaced by 1.0W + 2.0F. 2. In noncoastal A-Zones, 1.0W in combinations 4 and 6 shall be replaced by 0.5W + 1.0Fa 'The same E from Sections 1.4 and 12.4 is used for both Sections 2.3.2 and 2.4.1. Refer to the Chapter 11 Commentary for the Seismic Provisions. 7 |
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
Related questions
Question
100%
The roof of the Hartford Civic Center
located in Hartford, Connecticut
collapsed in the early morning of
January 18, 1978 after the area
experienced the largest snowfall in
the history of the five-year “old”
structure. Fortunately, no one was
injured in the collapse. However,
the center had been filled just a few
hours before the collapse with
spectators for a basketball game.
Immediately afterwards, an
investigation was begun to
determine the cause of the failure. A
suggested potential cause of the
failure was that the heavy snowfall
exceeded the design load. Your
task is to investigate this hypothesis.
Use the snow load handout provided and the applicable load combinations for strength design to determine the
required design total load for the roof of the structure.
Assume the following:
• The dead load on the roof was 35 pounds per square foot.
• The slope of the roof was less than 30 degrees, and the surface of the roof can be
classified as “all other” for the purposes of finding Cs.
• Ce = 1
Transcribed Image Text:-40
70
2500
20
(2500)
(1000)
40
MINIMUM DESIGN LOADS
(700)
40
CS
(1700
(800)
1200)
(700
HOO
500)
(500)
50 1900)
50
(600)
80
(500)
TO
Transcribed Image Text:2.1 GENERAL
Buildings and other structures shall be designed using
the provisions of either Section 2.3 or 2.4. Where
elements of a structure are designed by a particular
material standard or specification, they shall be
designed exclusively by either Section 2.3 or 2.4.
2.2 SYMBOLS
A = load or load effect arising from extra ordinary
event A
D = dead load
D; weight of ice
=
E = earthquake load
F = load due to fluids with well-defined pressures
and maximum heights
flood load
Fa
H = load due to lateral earth pressure, ground water
pressure, or pressure of bulk materials
L = live load
L,
roof live load
R = rain load
S = snow load
T = self-straining load
W
wind load
W; wind-on-ice determined in accordance with
Chapter 10
2.3 COMBINING FACTORED LOADS USING
STRENGTH DESIGN
2.3.1 Applicability
The load combinations and load factors given in
Section 2.3.2 shall be used only in those cases in
which they are specifically authorized by the appli-
cable material design standard.
2.3.2 Basic Combinations
Structures, components, and foundations shall be
designed so that their design strength equals or
exceeds the effects of the factored loads in the
following combinations:
1. 1.4D
2. 1.2D 1.6L + 0.5(L, or S or R)
3. 1.2D 1.6(L, or S or R) + (L or 0.5W)
4. 1.2D 1.0W+L+ 0.5(L, or S or R)
5. 1.2D 1.0E+L+ 0.2S
6. 0.9D1.0W
7. 0.9D+1.0E
EXCEPTIONS:
1. The load factor on L in combinations 3, 4, and 5 is
permitted to equal 0.5 for all occupancies in which
L, in Table 4-1 is less than or equal to 100 psf,
with the exception of garages or areas occupied as
places of public assembly.
2. In combinations 2, 4, and 5, the companion load S
shall be taken as either the flat roof snow load (p)
or the sloped roof snow load (p.).
Where fluid loads F are present, they shall be
included with the same load factor as dead load D in
combinations 1 through 5 and 7.
Where load H are present, they shall be included
as follows:
1. where the effect of H adds to the primary variable
load effect, include H with a load factor of 1.6;
2. where the effect of H resists the primary variable
load effect, include H with a load factor of 0.9
where the load is permanent or a load factor of 0
for all other conditions.
Effects of one or more loads not acting shall be
investigated. The most unfavorable effects from both
wind and earthquake loads shall be investigated,
where appropriate, but they need not be considered to
act simultaneously. Refer to Section 12.4 for specific
definition of the earthquake load effect E.'
Each relevant strength limit state shall be
investigated.
2.3.3 Load Combinations Including Flood Load
When a structure is located in a flood zone
(Section 5.3.1), the following load combinations shall
be considered in addition to the basic combinations in
Section 2.3.2:
1. In V-Zones or Coastal A-Zones, 1.0W in combina-
tions 4 and 6 shall be replaced by 1.0W + 2.0F.
2. In noncoastal A-Zones, 1.0W in combinations 4
and 6 shall be replaced by 0.5W + 1.0Fa
'The same E from Sections 1.4 and 12.4 is used for both Sections
2.3.2 and 2.4.1. Refer to the Chapter 11 Commentary for the Seismic
Provisions.
7
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